Abstract: In 2005–2006, the National Park Service’s Northern Colorado Plateau Network received funding to develop a revised checklist of the vascular plant flora of Natural Bridges National Monument. This entailed a thorough review of existing literature, re-examination of specimens from the Natural Bridges National Monument herbarium and other state and national museum collections, and additional field work to corroborate unverified species reports and locate new species. Based on this study, 428 vascular plant taxa have been confirmed or reliably reported as occurring in the monument (323 are known from validated herbarium specimens and 105 from unvouchered literature reports). Another 61 species formerly considered part of the monument flora have now been shown to be falsely reported. The current flora of Natural Bridges National Monument represents about 12% of the known flora of Utah and 25% of the flora of the Colorado Plateau ecoregion within Utah. At least 20 of these species are either formerly considered for federal listing as threatened, endangered, or sensitive, or are considered species of concern by the state’s natural heritage program. Introduced plants make up 11% of the monument flora (46 species), of which only two species are considered noxious weeds by the State of Utah. Further surveys in Natural Bridges National Monument are likely to find additional new species (about 126 are known from similar habitats outside the monument boundary), especially among lateseason flowering, weedy, or wetland taxa. This checklist includes updates from 2011-2012.